76 
JOURNAL  OR  HORTICULTURE  AND  COTTAGE  GARDENER. 
January  28,  1897. 
CHEMISTRY  IN  THE  GARDEN. 
(< Continued  from  page  48.) 
Nitrogen  (symbol  N). — This  element,  like  the  two  preceding 
it,  is  a  colourless  invisible  gas,  found  abundantly  in  Nature  in  a 
free  and  also  combined  state.  Free  nitrogen  forms  nearly  four- 
fifths  of  the  atmosphere,  and  combined  with  other  elements  it  is 
found  in  small  quantities  in  the  air  and  in  water,  and  in  larger 
quantities  in  soils,  plants,  and  animals.  Nitrogen  is  an  essential 
constituent  of  all  plants  ;  it  enters  into  the  composition  of  proto¬ 
plasm  and  other  organic  compounds  found  in  them,  protoplasm 
being  the  substance  which  is  the  living  part  of  plants. 
All  the  combined  nitrogen  on  the  earth  has  undoubtedly  been 
derived  from  the  free  gas  of  the  atmosphere.  The  free  nitrogen, 
although  present  in  such  large  quantities  in  the  air,  is  of  no  direct 
value  to  plants,  for  with  a  few  exceptions  they  cannot  assimilate  it. 
After  years  of  careful  research  and  numerous  experiments  it  has 
been  found  that  crops  depend,  with  the  exception  of  the  Legu- 
minosse,  upon  nitrogenous  compounds  in  the  soil  for  their  supply 
of  nitrogen,  and  that  plants  absorb  it  by  means  of  their  roots, 
chiefly  in  the  form  of  nitrates  ;  but  they  may  to  a  lesser  extent 
also  absorb  it  as  ammonium  salts.  When  we  purchase  nitrogenous 
manures  we  have  to  pay  from  6d.  to  9d.  a  pound  for  nitrogen  in 
the  form  of  ammonia,  and  from  9d.  to  Is.  for  nitrogen  in  the 
form  of  nitrates.  Seeing,  therefore,  how  important  ammonia  and 
nitrates  are  from  a  commercial  point  of  view,  we  should  do  well  to 
devote  a  little  of  our  time  to  their  study. 
Ammonia  (symbol  NH3). — This  substance  at  ordinary  tempera¬ 
tures  is  a  gas  possessed  of  a  pungent  odour,  having  an  alkaline 
reaction.  Ammonia,  as  we  may  see  by  its  chemical  formula,  con¬ 
sists  of  one  volume  of  nitrogen  chemically  united  with  three 
volumes  of  hydrogen.  If  equal  volumes  of  hydrogen  and  nitrogen 
were  weighed  we  should  find  that  the  latter  would  weigh  fourteen 
times  heavier  than  the  former.  In  ammonia  we  have  one  volume 
of  nitrogen  which  equals  14,  and  three  volumes  of  hydrogen 
which  equals  3  ;  the  weight  of  ammonia  gas  would  therefore  be 
seventeen  times  heavier  than  hydrogen  gaB,  equal  volumes  being 
taken.  As  these  varying  weights  may  be  a  little  puzzling  to  some 
of  our  readers  it  will,  perhaps,  be  advisable  before  proceeding 
further  to  give  a  table  of  the  elements  we  shall  have  to  consider, 
with  their  respective  weights  appended. 
Approximate  Weights  of  Elements. 
Elements. 
Weight. 
Elements. 
Weight. 
Hydrogen  ... 
1  . 
...  39 
Oxygen 
...  16  . 
...  24 
Nitrogen 
...  14  . 
...  40 
Carbon 
...  12  . 
...  56 
Sulphur 
...  32  . 
35J 
Phosphorus  ... 
...  31  . 
...  23 
Ammonia  being 
a  gas  the  gardener  could  not  apply  it  very  well 
in  that  form  to  his  plants  ;  but  seeing  it  has  an  alkaline  property, 
it  will,  therefore,  combine  with  acids  to  form  salts.  These  salts 
are  solid  substances,  of  which  the  following  may  be  taken  as 
examples  : — Ammonium  sulphate,  ammonium  nitrate,  and  ammo¬ 
nium  phosphate. 
Nitrates  are  salts  formed  by  the  chemical  union  of  nitric 
acid  (HNO3)  with  a  base.  The  alkaline  bases,  such  as  potash,  soda, 
lime  and  magnesia,  will  all  unite  readily  with  nitric  acid  to  form 
nitrates  of  potash,  soda,  lime,  and  magnesia,  and  these  substances 
are  of  considerable  value  to  gardeners  as  fertilisers.  Ammonia  and 
nitrates,  however,  will  be  dealt  with  more  fully  when  we  come  to 
consider  soils  and  manures  in  their  relation  to  plant  life. 
Carbon  (symbol  C). — This  substance  is  the  most  widely 
diffused  in  Nature  of  all  the  elements.  It  is  found  in  a  solid 
form,  and  nearly  pure,  in  the  diamond,  in  graphite,  and  in  charcoal. 
It  is  also  found  in  large  quantities  in  a  more  impure  state  in  coal. 
One  hundred  pounds  of  good  anthracite  from  South  Wales 
contains  92  73  lbs.  of  carbon,  3  36  lbs.  of  hydrogen,  and  3'91  lbs. 
of  oxygen  and  nitrogen.  Carbon  and  oxygen  unite  chemically  to 
forma  gas  called  carbonic  acid  gas  (C02).  This  acid  combines 
readily  with  the  base  lime  to  form  carbonate  of  lime  or  chalk,  a 
substance  which  occurs  in  considerable  quantities  on  the  earth.  On 
an  average  every  10,000  volumes  of  air  contains  four  volumes  of 
carbonic  acid  gas. 
All  parts  of  plants,  and  every  organic  compound  found  in 
them  contains  carbon.  Plants  obtain  their  carbon  from  the 
carbonic  acid  gas  of  the  atmosphere  by  means  of  their  leaves  ; 
and  submerged  water  plants  obtain  their  carbon  from  the  same 
gas  which  is  dissolved  in  water. — W.  D. 
(To  be  continued.) 
DEUTZIA  LEMOINEI. 
So  popular  are  the  several  species  and  varieties  of  Deutzias,  as  well 
for  flowering  in  the  open  as  for  forcing  for  winter  decoration,  that  a  new 
one  is  hailed  with  pleasure^  Several  months  ago  a  Deutzia  named 
Lemoinei  was  staged  at  the  Drill  Hall  by  Messrs.  Cripps  &  Son,  Tun¬ 
bridge  Wells,  and  to  which  the  Floral  Committee  adjudged  a  first-class 
certificate.  In  habit  the  plant  is  excellent,  being  dwarf  and  remarkably 
floriferous.  In  style  of  growth  it  favours  Deutzia  gracilis  in  many 
points,  but  the  snow  white  flowers  are  produced  on  stout  perpendicular 
growths  differing  from  the  well-known  pendent  habit  of  the  older 
variety.  The  woodcut  (fig.  21)  will  convey  an  idea  of  the  form  and 
manner  of  flowering  of  this  beautiful  plant. 
THE  DISCOLOURATION  OF  POTATOES. 
Having  read  with  much  interest  the  instructive  dissertations  given 
by  the  various  authorities  at  the  recent  Potato  Tercentenary  Conference, 
I  failed  to  find  particular  mention  of  that  all-important  affection  which 
unfortunately  still  reigns  paramount  throughout  the  kingdom,  if  not  in 
other  parts  of  the  Potato-producing  world.  I  allude  to  that  detrimental 
ailment — the  propensity  of  acquiring  a  discolouration  in  the  tissues  of 
the  tuber  when  grown  in  certain  soils  (assuming  that  the  nature  of  the 
soil  to  be  the  cause),  owing  presumably  to  a  deficiency  of  some  consti¬ 
tuent  necessary  for  the  production  of  good  and  mealy  Potatoes  free  from 
the  blemish  indicated,  and  which,  next  to  the  “disease,”  is  one  of  the 
most  undesirable  affections  to  which  the  “  noble  tuber  ”  is  heir. 
Various  theories  have  been  advanced  as  to  the  real  cause  and  nature 
of  the  ailment  in  question,  and  in  addition  to  that  pertaining  to  some 
chemical  constituent  deficiency  in  the  soil.  The  more  general  theory 
entertained  amongst  cultivators,  such  as  farmers  and  market  gardeners, 
is  that  founded  upon  the  supposition  that  it  is  the  effect  of  bruising 
the  tubers  through  rough  handling  when  gathering  and  storing  the  crop. 
Another  theory  is  entertained  that  it  arises  from  a  superheating  of  the 
tubers  when  stored  in  large  heaps  for  the  winter,  and  with  insufficient 
ventilation  or  other  provision  for  the  escape  of  the  steam. 
Obviously,  however,  such  theories  can  hardly  be  sustained,  con¬ 
sidering  that  the  ailment  in  question  affects  the  tubers  whilst  in  their 
growing  state,  yet  it  may  be  more  developed  by  the  storing  agency,  but 
hardly  by  bruising  from  rough  handling.  Moreover,  there  is  a  factor 
I  have  noticed  in  particular  appertaining  to  the  discolouration  indicated, 
and  which  I  opine  reaches  so  far  as  to  discount  the  storing  and  bruising 
theories  ;  it  is  to  the  effect  that  the  ailment  is  confined  chiefly  to  the 
base  of  the  tuber,  or  the  end  opposite  to  that  attached  to  the  roots  of 
the  plant — at  least,  such  is  the  initial  position  of  the  affection — and 
whence  it  gradually  spreads  throughout  the  economy  of  the  tuber 
according  to  circumstances. 
This  theory  may  be  speculative,  however,  and  is  subject  to  further 
proof,  unless  some  scientist  or  keener  observer  than  myself  is  already 
enabled  to  confirm  or  repudiate  it,  and  I  for  one  would  be  glad  to  learn 
if  something  more  definite  than  that  herein  advanced  can  be  adduced 
as  to  the  real  cause  and  nature  of  the  matter  in  question.  I  forgot  to 
mention  that  an  excess  of  humus  or  nitrogenous  pabulum  in  the  soil  has 
been  suggested  as  a  probable  agent  in  the  production  of  the  ailment. 
In  conclusion  1  may  remark  that  during  the  present  winter  I  have 
procured  samples  of  Potatoes  from  several  growers  and  districts  sup¬ 
plying  the  Birmingham  market  by  way  of  a  test,  and  have  found  the 
majority  of  the  samples  more  or  less  affected  by  the  phenomenon — the 
subject  of  the  foregoing  remarks. — W.  G. 
HE  PATIO  AS. 
The  common  Hepatica  in  its  several  varieties  has  been  an  admired 
denizen  of  gardens  for  a  long  period.  Parkinson  describes  no  less  than 
ten  sorts,  of  which  some  at  least  are  still  in  cultivation.  They  were 
known  also  as  Liverworts,  under  the  botanical  appellation  of  Hepatica 
trifolia,  the  specific  name  after  a  time  being  superseded  by  the  more 
correct  “  triloba.”  The  latter  designation  was  changed  by  Linnaeus,  by 
whom  the  plant  was  renamed  Anemone  hepatica  ;  but  this  appears  to 
have  been  received  with  little  favour  by  gardening  writers,  and  even 
now  few  recognise  the  plant  under  that  name.  In  the  “  Paradisus  ” 
three  white  varieties  are  described — “  the  lesser  white,”  which  I  take  to 
be“nivea”  of  Loudon;  “the  great  white,”  and  “the  white  with  red 
threads,”  which  is  Loudon’s  “  red-anthered  white,”  or  alba.  The  last 
named  is  the  sort  generally  sold  by  nurserymen  for  the  single  white. 
This  with  the  other  two  I  have  grown  for  many  years.  There  are  also 
three  blue  varieties  mentioned.  One  of  these  is  “  blew  tending  to  violet 
purple.”  Parkinson’s  red  Hepatica  is  “  of  a  bright  blush,  or  pale  red 
colour,  very  pleasant  to  behold,  with  white  threads  or  chives  (anthers) 
in  the  middle  of  them.” 
Another  variety  is  “  the  ash-coloured  or  argentrive,”  notice  of  which 
I  have  found  nowhere  else.  The  flowers  are  much  larger  than  those  of 
the  others.  I  have  two  varieties  of  H.  angulosa,  which  are  in  respect  of 
habit,  size  of  foliage,  and  flower  distinct  from  each  other,  though  similar 
in  colour.  Is  it  not  possible  that  one  of  these  may  be  the  argentrive  1 
Of  double  varieties  only  two  are  named,  both  of  which  are  still  cultivated. 
